The present invention pertains to acetabular reamers, and more particularly, to acetabular reamer cups.
Acetabular reamers are used by surgeons to prepare pelvic bones and the like for insertion of artificial joints. An acetabular reamer is rotated to cut a cavity into the bone into which the socket portion of the artificial joint can be inserted. Dimensions and shape of the cavity cut are critical as the tolerances between the cavity and the socket portion of a joint must be small to insure proper function. This is especially true with the newly available "cementless" hip joints. Before "cementless" hip joints, the socket portion of the joint was cemented into the cavity. In the "cementless" joint, the socket portion is frictionally fit into the cavity, placing new importance upon accurate cavity dimensions and tolerances.
In the past methods of making acetabular reamer cups, holes in the cup were countersunk from the inside and then a part of the edge of the hole was pushed up and subsequently hand sharpened. This process is slow and very dependent upon the skill of the individual workman sharpening the edges. The acetabular reamer cup produced by that method has edges sharpened to a double bevel and as a result, the edges stay sharp only a relatively short period of time. Another method of producing an acetabular reamer is disclosed in U.S. Pat. No. 4,811,632 in which holes in the cup are deformed outwardly of the exterior surface to provide a cutting portion of the hole margin, smoothing the outer surface of the cup to sharpen the cutting portions, and subsequently raising the curved cutting edges from the cutting portions outwardly of the surface. This method provides an acetabular reamer cup that has edges sharpened to a single bevel and as result the edges stay sharper than the prior described method, but the method includes multiple steps, and the deforming and smoothing steps do not produce an acetabular reamer cup with uniform cutting edges or exceedingly tight dimensions and/or tolerances.
Additionally, in utilizing prior acetabular reamer cups, surgeons have experienced slow cutting speeds, a requirement of considerable strength to force the reamer cup against the bone to be cut, and thermal osteonecrosis all of which should be minimized or eliminated.
It is therefore highly desirable to provide an improved acetabular reamer cup and method for making the same.
It is also highly desirable to provide an improved acetabular reamer cup which is capable of more accurate cavity dimensions and smaller tolerances, and an improved method for making the same.
It is also highly desirable to provide an improved acetabular reamer cup which minimizes thermal osteonecrosis and an improved method for making the same.
It is also highly desirable to provide an improved acetabular reamer cup which cuts faster and requires less force against the bone than prior acetabular reamer cups, and an improved method for making the same.
It is also highly desirable to provide an improved method for making acetabular reamer cups which has less productions steps than prior methods.
It is also highly desirable to provide an improved method for producing an acetabular reamer cup that is faster cutting and more economical to manufacture than past methods and which provides a cup which has improved tolerances and improved cutting edges.
Finally, it is highly desirable to provide an improved acetabular reamer cup and method for making the same which possess all of the above desired features.